Sizing compositions



Patented Jan. 15, i946 SIZING COMPOSITIONS Robert T. Mashburn,Kalamazoo, Mich., assignor to Hercules Powder Company,

Wilmington,

DeL, a corporation of Delaware No Drawing. Application December 11, 1941, Serial No. 422,520

' 18 Claims. (01. 106-143) for sizing purposes, in recent years it has been realized that improved sizing efiiciency and substantial manufacturing economies could be obtained by the use of rosin size dispersions in which practically at; of the rosin is present in free, i. e.,

unsaponifled, form. Accordingly, a number of i5 sizing compositions of this general type have been proposed, and while several of such compositions have enjoyed moderate commercial usage, they have certain disadvantages which prevent their general acceptance throughout the sizing art. For 20 example, in U. 5. Patent No. 2,116,788 it has been proposed to prepare high free rosin size dispersions by treating an aqueous solution of saponified rosin with a protein, e. g., milk casein or soya bean protein, which hydrolyzes the saponified rosin to form an emulsion or suspension comprising free rosin and an alkali proteinate. The suspension is then treated with an acid or acid salt, such as boric acid, aluminum sulphate, acetic acid, mono-sodium phosphate, etc., to extend the hydrolysis reaction and to neutralize the alkali proteinate. Such sizes, however, seldom contain more than 70 per cent of the rosin in free form,

- and, as a result of an acid or acid salt having been used to extend the hydrolysis reaction and to neutralize the alkali proteinate, contain considerable amounts of neutral inorganic salts, e. g., sodium borate, sodium sulphate, sodium phosphate, etc., which detract from sizing emciency.

Similarly it has been proposed in U. S. Patent No. 1,882,680 to agitate molten rosin with an aqueous alkaline solution of a protective colloid such as casein, whereby there is formed a high free rosin paste size which may be diluted to the usual siz-- ing concentration. This size likewise has the disadvantage in that not all of the rosin is in free form and that it contains substantial amounts of alkali which must be neutralized before the size can be precipitated on the paper fibers.

It is accordingly an object of this invention to provide non-alkaline aqueous rosin sizing compositions in which substantially all of the rosin is present in free form.

A further object is to provide aqueous rosin sizefilciency with minimum'consumption of papermakers alum or other coagulant.

A further object is to provide aqueous rosin sizing compositions which are substantially free from neutral inorganic salts. I

A still further object isto provide non-alkaline aqueous dispersions of free rosin which do not coagulate upon repeated freezing.

Other objects will be apparent from the following detailed description of the invention and various advantages'not specifically referred to herein will occur to those skilled in the art upon employment of the invention in practice.

In accordance with the above objects, I have found that free rosin may be dispersed in water with non-alkaline dispersing agents and that the dispersions so formed may be rendered stable by means of non-alkaline protective colloids. Inasmuch as both the dispersing and stabilizing agents are non-alkaline, i. e., neutral or slightly acid, it is manifest that practically all of the rosin will be present in free form and that a minimum amount of paper-maker alum or other acid coagulant will be required to precipitate the size on the paper fibers. Accordingly, the rosin size dispering compositions which permit maximum sizing sions provided by the present invention are entirely free from the disadvantages associated with the free rosin size dispersions heretofore known, and in many instances provide a degree of sizing considerably better than that provided by such prior art sizes. They are further characterized by excellent stability to fioccing upon dilution with hard water.

The rosin employed in preparing my new sizing compositions may be any of the grades of refined wood or gum rosin, or it may be a mixture of gum and wood rosins. Alternatively, it may be a rosin which has been subjected to heat-treatment to reduce its tendency to crystallize and form acid abietate salts, but insufflcient to reduce its'tendency to crystallize, or it may be rosin which has been hydrogenated to render it stable to discol oration and oxidation in the air.

Any non-alkaline orgfianic dispersing agent may be employed to maintain the rosin in aqueous dispersion, although it will generally be found preferable to employ a sulphonated fat or oil, such as sulphonated castor oil, sulphonated stearin, sulphonated linseed oil, sulphonated fish oil, etc. However, other neutral dispersing agents, such as triethanolamine oleate, alkylaryl sulphonic acid salts, sulphonated higher fatty alcohols, etc., may be employed if desired. The proportion of the dispersing agent required for dispersing the rosin depends somewhat upon the between about 2 and about particular agent employed. but will usually be 10 per cent by weight or the rosin.

The protective colloids employed as stabilizing agents for the aqueous rosin dispersions are prelerably substantially neutral proteinaceous materials, such as milk casein, egg albumin, soya bean protein, etc., although other colloidal substances, e. g., gum arabic, starch, water-soluble 2,sos,17a 1 were heated to a temperature of about 100 C..

and 22.5 pounds of 75% sulphonated castor oil throughout the molten rosin, 15 pounds of casein in the form of a neutral 15% by weight aqueous suspension were gradually added with vigorous agitation, after which the resulting paste was diluted with 242 pounds of water. Approximatemethyl cellulose, etc., may be employed if delo ly 20 pounds of the size dispersion so prepared sired. The proportion of the protective colloid (equivalent to 9 pounds of rosin) were employed required to stabilize the dispersion is somewhat to size a. paper furnish consisting of 350 pounds dependent on the proportion of dispersing agent of unbleached sulphite pulp and 1,000 pounds of employed as well as upon the degree of stability old paper stock. The paper prepared from the desired. Ordinarily, however, it will be found 15 sized furnish had a basis weight (500 24 x 36 satisfactory to employ the protective colloid in sheets) of 41.5 pounds, a Gurley densometer an amount between about 1 and about 25, prefporosity value of 113 secs., a sugar dye water erably between about and about 20, per cent penetration value of about secs, and an ink by weight of the rosin and in the form of a relaflotation value of 20 secs. In contrast, a paper tively concentrated, e. g., -20 per cent by weight, prepared from a similar furnish which had been aqueous dispersion. sized with 12.7 pounds of a 12% free rosin paste According to a preferred mode or preparing the size (equivalent to 12 pounds of rosin) had a basis sizing compositions provided by the invention, the weight of only 40.5 pounds, a Gurley densomcter rosin is melted and the desired amount of the porosity value of 122 secs., a water penetration dispersing agent is added with suiiicient agitation 25 value of about 11 secs. and an ink flotation value to form a homogeneous molten mass. A substanof 28 secs. tially neutral or slightly acid aqueous solution or EXAMPLE 3 dispersion of the protective colloid is then added gradually with rapid stirring, whereby there is pproxlmaielv 150 Parts by Weight of K Wood produced a high solids paste type dispersion 30 rosin, which had previously been heat-treated which can readily be diluted with water to a solids at temperature of ablmt length concentration between about and about 60 per of sufficient to reduce its tendency to cent by weight. acid abietate salts but insufficient to reduce its The following examples Wm illustrate several crystallizability, i. e., until its solid optical rotaways in which the principle of the invention has 35 was value Of abut was been applied, but are not to be construed as limitmelted by heatmg to a temperature of about mg the Same 105 C. Approximately 10 parts by weight of sul- EXAMPLE 1 ionated castoroil were then gradually stirred A roximatel 800 ms b Wei ht of G into the molten rosin, after which parts by rosi was melteii by li e ting to a timperaturi 40 Weight of a per aqlleous dispersion of about 100 C., after which 40 parts by weight of Qasem were adqed rapidly with gm-01.15 agita" 75% sulphonated castor oil was gradually added mixture was then mlxed w with stirring. Stirring was continued for several 12 patts w of wate? to obtain a minutes to insure uniform dispersion of the sulpaste which could t be dlluted to ordi' phonated castor oil in the molten rosin, during El g g g cozmentratmns slmply by the addiion 0 0 We er. giggi g: the fi? of the F was The following Table Lpresents data illustrative at about 100 C. Approximately 192 parts by weight of an aqueous casein solution of the 5mm gmciepcy of Slze dlspersmn having a pH of about 6 and containing 163% pared as described in Example 1, as compared to by weight of casein was then gradually added with that of several commercial sizes. Ineach experirapld stirring to the molten mixture of rosin and ment' 100 per cent bleached sulphlte pulp was sulphonated castor n after which the mixture beater-sized with sufilcient size to provide 1 per was diluted with 400 parts of water. The comcent rosin, based on the Weight of dry pulppositlon so obtained was a stable, substantially Handsheets were then run from the sized P neutral rosin dispersion containing about by and after drying and conditioning e Sheets weight of solids. A particle size determination were subjected to the sizing tests indicated in the showed that 40% of the dispersed particles were table.

Table l mgg S itZFG'tttE" iiiiii ilitt cit'fiie x 36 sheets) test, secs. test, secs. test, secs.

1 Size prepared as in Example I 7 Commercial dry size 30. 4 23- 0 22. 3 l3. 7 3 Commercial paste size containing 17.2 per cent rosin in free forum. 30. l 24. 0 24. 5 l4. 7 Size prepared according to U. S. 1,882,680 31 2 15. 5 36. 0 Size prepared according to U. S. 2,116,768 32-0 18.6

smaller than one micron, 10% were larger than 3 microns, and practically none were larger than five microns. After storage in glass at 80 F. for 4 months, a second size determination showed that little change in particle size had taken place.

Exsnrrr2 Approximately 300 pounds of G gum rosin While the free rosin sizing dispersions provided by the invention have good mechanical stability in that they do not tend to coagulate or break upon long standing at room temperatures, and are stable to fleecing upon dilution with hard water, they are rather sensitive to freezing, i. e., they freeze and break at temperatures not far below the freezing point of water. While this characteristic is of no significance during the summer months or in southern parts ot-the country, in northern climates it constitutes a considerable disadvantage. I have found, however, that the dispersion may be stabilized against freezing by the addition of a small proportion oi one or more of the materials: dried whey, sugar, corn syrup, glycerol, and ethylene glycol. These materials not only lower the freezing point of the dispersion but also stabilize it against coagulation upon repeated freezing at temperatures as low as -l F. to -23 F. for as long as 16 hours. Accordingly, the sizing dispersions stabilized in this manner may be shipped as stored under alternate conditions of freezing and thawing over long periods of time without danger of coagulation.

Ordinarily, the above-mentioned stabilizing agents are simply added to the finished dispersion in the form of an aqueous solution, although if desired they may be incorporated in the dispersion during its preparation as hereinbefore described. Usually, they are employed in an amount representing between about 2 and about 10, preferably about 6, per cent by weight of the dispersion, although the exact amount will depend upon the particular stabilizing agent, the concentration of the dispersion, and. the degree of stability desired.

The following Table II presents data illustrating the degree of stability to coagulation upon freezing secured through the use of'certain oi the above-mentioned stabilizing agents. In each experiment the designated stabilizing agent in the form of an aqueous solution was added in the inheated proportion to a sample 01 the sizing dispersion prepared in Example 1. The stabilized dispersions were then completely frozen by exposure to temperatures within the range of about F. to -23 F. for 16 hours, after which they were allowed to return to room temperature over a period of 8 hours. This treatment, referred to in,the table as a cycle, was repeated until the dispersion broke or until it resisted coagulation through ten cycles.

Table II Stabilizing agent Stability Experiment No.

Name Amount 1 None 2 Dried whey. .ri0

Broke on lst cycle. D

Stab1l)e to 10 cycles.

0. Broke on lst cycle. Broke on 2nd cycle. Stab1l)e-to 10 cycles.

0. Broke on lst cycle. Broke on 2nd cycle. Stabg to 10 cycles.

1 Per cent by weight of dispersion.

It will be noted from the above table that although the unstabilized dispersion breaks on the first cycle, the use of only small amounts of the stabilizing agents provides resistance to coagulation through at least ten cycles. Such a degree of resistance is suflicient to withstand the most severe conditions to which the dispersion might be exposed during shipment or storage prior to use. The presence of the stabilizing agent in no way detracts from sizing efilciency, and the stabilized dispersions retain all of the hereinbeiore mentioned advantageous characteristics of the unstabilized dispersions.

o. Broke on 3rd cyclev This application is a continuation-in-part of my co-pending application Serial No.'2'82,201, filed June 30, 1939.

What I claim and desire to protect by Letters Patent is:

1. A stable nonalkaline paper sizing composi- 2. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% or a nonalkaline organic dispersing agent for the rosin, based on the weight of-the rosin, in a nonalkaline aqueous medium comprising water and between about 1 and about 25% of a protective colloid, based on the weight of the rosin, said sizing composition being substantially free of rosin soap.

3. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% 01 a nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water and between about 1 and about 25% of a protective colloid, based on the weight of the rosin, said sizing composition being substantially free of rosin soap and containing between about 40 and about 60% by weight of solids.

4. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glyceride oil in a nonalkaline aqueous medium comprising water and between about 1 and about 25% of a protective colloid, based on the weight of the rosin, said sizing composition being substantially free of rosin soap.

5. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glyceride oil in a nonalkaline aqueous medium comprising water and be tween about 1 and about 25% of a protective colloid, based on the weight of the rosin, said sizing composition being substantially free of rosin soap and containing between about 40 and about 60% by weight of solids.

6. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and a nonalkaline organic dispersing agent for the rosin in an amount sufiicient for dispersing the rosin, in a nonalkaline aqueous medium comprising Water and between about 1 and about 25% of a proteinaceous protective colloid, based on the weight of the rosin, said sizing composition being substantially free of rosin soap.

7. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glyceride oil in a nonalkaline aqueous medium comprising water and between about 1 and about 25% of casein, based on the weight of the rosin, said sizing composition being substantially free of rosin soap.

8. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sultonated glyceride oil in a nonalkaline aqueous medium comprising water and betwe'en about 1 and about 25% of casein, based on the weight of the rosin, said sizing composition being substantially free of rosin soap and containing between about 40 and about 60% by weight of olids.

9. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about of sulfonated castor oil in a nonalkaline aqueous medium comprising water and between about 1 and about 25% of casein, based on the weight of the rosin, said sizing composition being substantially free of rosin soap.

10. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of sulfonated castor oil, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water and between about 1 and about 25% of casein, based on the weight of the rosin, said sizing composition being substantially free of rosin soap and containing between about 40 and about 60% by weight of solids.

11. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and a nonalkaline organic dispersing agent for the rosin in an amount sufiicient for dispersing the rosin, in a nonalkaline aqueous medium comprising water, a protective colloid in an amount sufficient to stabilize the dispersion, and an agent selected from the group consisting of dried whey, sugar, corn syrup, glycerol, and ethylene glycol, said agent being present in an amount sufficient to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of to -23 F. for 16 hours, said' sizing composition being substantially free of rosin soap.

12. A stable nonalkaline paper sizing composition consisting essentially of adispersion of free rosin and between about 2 and about 10% of a nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water, between about 1 and about of a protective coiloid, based on the weight of the rosin, and between about 2 and about 10% by weight of the dispersion of an agent selected from the group consisting, of dried whey, sugar, corn syrup, glycerol, and ethylene glycol, said agent rendering the dispersion stable to coagulation upon repeated freezing at temperatures in the range of 15 to -23 F. for 16 hours, said sizing composition being substantially free of rosin soap.

13. A stable nonalkaline paper sizing composition -consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of a protective colloid, based on the weight of the rosin, and about 6% of dried whey, based on the total weight of the rosin dispersion, said dried whey serving to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of -15 to 23 F. for 16 hours, said sizing composition being substantially free of rosin soap.

14. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of tree rosin and between about 2 and about 10% of a nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of a protective colloid, based on the weight of the rosin, and about 6% of sugar, based on the total weight of the rosin dispersion, said sugar serving to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of 15 to -23 F. for 16 hours, said sizing composition being substantially free of rosin soap.

15. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of a protective colloid, based on the weight of the rosin, and about 6% of corn syrup, based on the total weight of the rosin dispersion, said corn syrup serving to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of 15 to 23 F. for 16 hours, said sizing composition being substantially free of rosin soap.

16. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glyceride oil in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of casein, based on the weight of the rosin, and an amount of dried whey sufiicient to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of 15 to 23 F. for 16 hours, said sizing composition being substantially free of rosin soap.

17. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glycerine oil in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of casein, based on the weight of the rosin, and an amount of sugar suflicient to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of 15 to -23 F. for 16 hours, said sizing composition being substantially free of rosin soap.

18. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glyceride oil in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of casein, based on the weight of the rosin, and an amount of corn syrup suflicient to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of 15 to -23"' F. for 16 hours, said sizing composition being substantially free of rosin soap.

ROBERT T. MASHBURN. 

